Leptin is the name given to the product of the "ob" gene. A defect in "ob" gene or in its receptor leads to genetic forms of obesity in rodents. Although mutation in leptin gene has not been identified in obese humans or in patients with NIDDM, such genetic defects may explain rare causes of familial obesity in humans. However, it is much more likely that a disturbance in leption secretion may be a contributory factor to human obesity. Because of enormity of the problem of obesity in the United States, this issue is of urgent clinical relevance. This study is a pilot study in lean and obese healthy normal subjects. The aim of this study is to study postprandial response to leptin levels and its relationship to hunger and satiety in lean and obese humans.